On further reduction of \(l_\theta \) , particles dynamics inside the cavity become completely diffusive. Recall that this regime is characterized by the restriction, \(l_{\theta } \ll \delta \phi R\) . For well separated opening windows, the exit process through one window is not affected by the other adjacent pores. Thus, total exit rate can be expressed as a sum of the exit rate through individual windows. This leads to, \(\tau _{ex} = \tilde{\tau }_{ex}/2\) . Where, \(\tilde{\tau }_{ex}\)  is the mean exit time through one opening when the other windows are closed. On the other hand, when the exit points are not well separated, a logarithmic dependence of \(\tau _{ex}\)  on the chordal distance between pore centers is observed [1]}
\(\tau _{ex} = \frac{2R^2}{2D_0+l_\theta v_0}\left[\ln \left(\frac{2\pi R}{\lambda }\right)+\tilde{\chi }\right]. \) 
